Conformal microstrip printed antenna K. Elleithy H. Bajwa A. Elrashidi (elleithy@bridgeport.edu ) (hbajwa@bridgeport.edu ) (aelrashi@Bridgeport.edu ) University of Bridgeport 126 Park Avenue Bridgeport, CT 06604 Abstract In this paper, the comprehensive study of the conformal microstrip printed antenna is presented. The main advantages and drawbacks of a microstrip conformal antenna are introduced. The earlier researches in cylindrical- rectangular patch and conformal microstrip array are summarized. The effect of curvature on the conformal Microstrip antenna patch on conical and spherical surfaces is studied. Some new flexible antenna is given for different frequencies. Finally, simulation software is used to study the effect of the curvature on the input impedance, return loss, voltage standing wave ratio, and resonance frequency. Keywords: Microstrip antenna, conformal antenna, Printed antenna, resonance frequency, curvature, input impedance, return loss, and voltage standing wave ratio. 1. Introduction Microstrip antennas have been widely studied in recent years. The main reasons are due to a plethora of reasons, such as low profile, lightweight, low cost, high gain and conformability to curved surfaces [1]. Planner microstrip antennas have been extensively studied and the models used to analyze this type of antenna have reached some kind of maturity. Conformal microstrip antennas are very important in many applications such as mobile communication, airplane, rockets, radar and satellites [2]. Conformal antennas are mainly the following advantages over the planer microstrip antennas [3]: 1. Conformal antennas have little effect of carrier’s own aerodynamic properties due to its conformal surface. 2. Conformal antennas can be used to simplify the antenna installation under the conditions of assuring the performance of the antenna. 3. Conformal antennas can eliminate or reduce the error caused by radome. The radome does not need to install; even if the radome is installed, as the microstrip antenna and its close proximity, distortion of the antenna is greatly reduced [4]. 4. With planer arrays the radiation pattern changes with the direction of scan, while conformal arrays with rotational symmetry (cylindrical profile) can have scan-invariant pattern [5]. 5. Cylindrical conformal gives nearly Omni- directional radiation pattern [6]. 6. It gives large angle coverage. Because of the advantages of conformal antennas, it is very popular in the different flight aircrafts [7]. On the other side, a conformal microstrip antenna has some drawbacks due to bedding [8], those drawbacks are illustrated below: 1. The dielectric material will undergo stretching and compression along the inner and outer surfaces, respectively. Stretching of copper traces will result in phase, impedance, and resonance frequency error. 2. Shaping the material can also result in a change in both the dielectric constant and material thickness. The thickness is an easily measured parameter, and measuring the dielectric constant of a cylindrical shaped substrate can be done using the two microstrip line method [9]. 3. Dielectric materials will suffer from cracking due to bending and that will affect the performance of the conformal microstrip antenna. A better method for creating uniform cylindrical structures would be to roll the material into a cylindrical shape while the outer surface is still completely plated, then pattern and each the material in its cylindrical configuration. In the next sessions, we will show some earlier research in conformal mirostrip antenna field. 2. Cylindrical-Rectangular Patch Antenna Cylindrical-rectangular patch is the most famous and popular conformal antenna. The manufacture of this antenna is very easy with respect to spherical and conical antenna especially in the military field. So the research in this type of conformal antenna stared early by 1980’s [10].